KR101696113B1 - Wire rod enabling omitting heat treatment, method for manufacturing same and method for manufacturing steel wire using the same - Google Patents

Abstract

Disclosed are a wire material containing at least 30% of an area (having 100% of the area) of martensite, a method for manufacturing the wire material, and a method for manufacturing a steel wire using the wire material and the method. The wire material comprises: 0.1-0.2 wt% of carbon (C); 0.1-0.5 wt% of silicon (Si); 5-8 wt% of manganese (Mn); 0.03 wt% or less of phosphorous (P); 0.03 wt% or less of sulfur (S); 0.001-0.003 wt% of boron (B); 0.004 wt% or less of nitrogen (N); and the balance of iron (Fe) and inevitable impurities.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a wire rod which can be subjected to heat treatment, a manufacturing method thereof, and a method of manufacturing a steel wire using the wire rod,

More particularly, the present invention relates to a wire rod for an armor cable capable of omitting a heat treatment, a method for manufacturing the wire rod, and a manufacturing method of the steel wire using the wire rod. ≪ / RTI >

The armor cable is a reinforcing material that supports the load applied to the flexible pipe that transports the crude oil at sea, and should have excellent hydrogen resistance (HIC) and fatigue characteristics. Strength is important because armor cables are used because armor cables support intermediate stainless steel pipelines. Also, since the oilfield sampling environment changes from the continental shelf to the deep sea, a long-length armor that can be used in deep water is needed, which is only possible by increasing the strength. The reason why the hydrogen resistance should be high is because it is indirectly influenced although it does not directly contact with the oil well, and furthermore, when the S content in the oil well is high, more hydrogen resistance is required. The fatigue characteristics are due to the fact that their use environment is placed in a dynamic fatigue environment rather than a static environment, and it is known that they are in proportion to the strength in general.

Up to now, the steel types applicable to armor cables are general steel products with carbon content of 0.3 to 0.8 wt%. The other components are Si of 0.2 to 0.3 wt% and Mn of 0.3 to 0.6 wt%, P And S are not more than 0.015 wt% and not more than 0.012 wt%, respectively, which are typical levels.

On the other hand, the reason why the carbon content of the product used for the armor cable is 0.3 to 0.8% by weight is to form a fine pearlite structure through heat treatment and to increase the fraction thereof. This is because the fine pearlite structure can improve the strength most effectively during the drawing process. However, products using such a pearlite structure have a disadvantage in terms of economical efficiency since they must necessarily perform a preheating treatment for microstructure.

One of the objects of the present invention is to provide a wire capable of omitting the heat treatment, a method for manufacturing the wire, and a method for manufacturing a steel wire using the wire.

In order to accomplish the above object, according to one aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: 0.1 to 0.2% of C, 0.1 to 0.5% of Si, 5 to 8% of Mn, 0.001 to 0.003% of B, 0.004% or less of N, and the balance Fe and unavoidable impurities, and 90% or more (including 100% by area) of martensite.

In another aspect of the present invention, there is provided a ferritic stainless steel comprising 0.1 to 0.2% of C, 0.1 to 0.5% of Si, 5 to 8% of Mn, 0.03% or less of P, 0.03% or less of S, To 0.003%, N: 0.004% or less, the balance Fe, and unavoidable impurities; subjecting the reheated billet to hot rolling to obtain a wire material; winding the wire material; To 850 DEG C at a rate of 1 DEG C / sec or less (excluding 0 DEG C / sec), and secondarily cooling the primary cooled wire to 200 DEG C at a rate of 10 DEG C / sec or more The present invention provides a method of manufacturing a wire rod.

In another aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: 0.1 to 0.2% of C, 0.1 to 0.5% of Si, 5 to 8% of Mn, 0.03% or less of P, 0.001 to 0.003% of N, 0.004% or less of N and the balance Fe and unavoidable impurities; subjecting the reheated billet to hot rolling to obtain a wire rod; winding the wire rod; Cooling at a rate of 1 DEG C / sec or less (excluding 0 DEG C / sec) to 500 to 850 DEG C, and secondarily cooling the primary cooled wire to 200 DEG C at a rate of 10 DEG C / sec or more, Removing the scale formed on the surface of the secondarily cooled wire to secure the dimensional accuracy of the wire after the wire has been secured and securing the dimensional accuracy of the wire with a total reduction amount of 66% or more at a drawing speed of 100 m / And rolling to obtain a steel wire.

As one of various effects of the present invention, there is an advantage that a steel wire excellent in strength and ductility can be secured even if the heat treatment is omitted.

1 (a) and 1 (b) show the surface of the wire according to the inventive example 1 and the comparative example 1, respectively.

Hereinafter, a wire material capable of omitting the heat treatment which is one aspect of the present invention will be described in detail.

First, the alloy composition and the composition range of the wire rod will be described in detail. It is to be noted that the content of each component described below is based on weight unless otherwise specified.

Carbon (C): 0.1 to 0.2%

Carbon improves the strength of the steel. In order to obtain such effects in the present invention, the carbon content is preferably 0.1% or more. However, when the content is excessive, plate-shaped martensite is formed and disconnection may occur during rolling, which is not suitable. In order to prevent this, the carbon content is preferably 0.2% or less, more preferably 0.15% or less.

Silicon (Si): 0.1 to 0.5%

Silicon is dissolved in ferrite to inhibit carbide formation. On the other hand, it is known that the strength of steel is improved when silicon is added. Generally, when 0.1% silicon is added, the strength is improved to 14 ~ 16 MPa level. In order to obtain such effects in the present invention, the carbon content is preferably 0.1% or more. On the other hand, when the silicon content exceeds 0.5%, the effect of increasing the strength is not large, so the upper limit is set to 0.5%.

Manganese (Mn): 5 to 8%

Manganese exists in solid form as a solid solution in a microstructure, and is added to increase the strength and ensure entrapment. In particular, when manganese is added to the range to be controlled in the present invention, it is possible to form needle-shaped martensite only by air-cooling in the stelmo core. If the content is less than 5%, it may be difficult to secure the target strength. On the other hand, when the content exceeds 8%, manganese segregation occurs severely and delamination may occur in the longitudinal direction during rolling.

0.03% or less phosphorus (P) and 0.03% or less sulfur (S)

Phosphorus and sulfur are inevitably impurities contained in the steel. In the present invention, the content thereof is not specially specified, but the upper limit thereof is controlled to 0.03% or less from the viewpoint of ensuring sufficient ductility.

Boron (B): 0.001 to 0.003%

Boron is an element that has a strong quenching effect with manganese and is an essential element added to obtain martensite as a main structure of wire rods. In order to obtain such effects in the present invention, the content of boron is preferably 0.001% or more, more preferably 0.0012% or more. However, when the content is excessive, it does not exist as solid solution B in the steel, and it forms a coarse BN or the like on the grain boundary, which may adversely affect the ductility of the steel. In order to prevent this, the content of boron is preferably 0.003% or less, more preferably 0.0025% or less.

Nitrogen (N): Not more than 0.004%

Nitrogen is an inevitably contained impurity, and is an element which is a main cause of reduction in ductility due to being dissolved in ferrite. Therefore, it is preferable to control the content to be as low as possible. In theory, it is advantageous to control the nitrogen content to 0 wt%, but it is inevitably contained inevitably in the manufacturing process. Therefore, it is important to manage the upper limit, and in the present invention, the upper limit of the nitrogen content is controlled to 0.004%.

The balance other than the alloy composition is iron (Fe). In addition, the wire of the present invention may include other impurities which can be normally included in the industrial production process of steel. These impurities can be known to anyone with ordinary knowledge in the art to which the present invention belongs, so that the kind and content of the impurities are not specifically limited in the present invention.

The wire of the present invention has martensite as a main structure and may include martensite of 90% or more (including 100% or more area), more preferably 95% or more (100% or more area ) Of martensite. By securing the above-described structure, the wire material of the present invention is excellent in ductility and excellent in workability.

According to one example, the average circle equivalent diameter of the martensite may be 15 m or less. If the average circle-equivalent diameter exceeds 15 탆, there is a fear that disconnection may occur during processing.

The wire rod of the present invention described above can be manufactured by various methods, and the production method thereof is not particularly limited. However, as an embodiment, it can be produced by the following method.

Hereinafter, a method of manufacturing a wire rod capable of omitting a heat treatment, which is another aspect of the present invention, will be described in detail.

First, the billet satisfying the above-mentioned component system is reheated. This step is a step to dissolve the (Fe, Mn) ₂₃ C ₆ carbide formed in the grain boundaries and inhibit the formation.

According to one example, during reheating of the billet, the reheating temperature may be between 1150 and 1250 ° C. As the temperature of the austenite single phase range and the reverse austenite grains are not coarsened, an effective temperature in the removal of residual (Fe, Mn) ₂₃ C ₆ carbide. If, in the case where the reheating temperature is lower than 1150 ℃ will be for a longer time required for the melting of the (Fe, Mn) ₂₃ C ₆ carbide remains, the final microstructure formed after cooling is caused coarsening of austenite grains accordingly There is a tendency to coexist. On the other hand, when the reheating temperature exceeds 1250 DEG C, austenite grain coarsening is also caused and the final microstructure formed after cooling tends to be coarsened.

According to one example, during reheating of the billet, the reheating time may be from 90 to 150 minutes. If the reheating time is less than 90 minutes, the (Fe, Mn) ₂₃ C ₆ carbide may not be sufficiently melted, while if the reheating time exceeds 150 minutes, there is a fear that the austenite grains will be coarsened have.

Next, the reheated billet is hot-rolled to obtain a wire rod.

According to one example, during hot rolling, the finish rolling temperature may be 1000 ° C or higher. If the finishing rolling temperature is less than 1000 캜, impurities may be formed due to deformation during rolling, and there is a possibility that the possibility of precipitation of carbides on the intergranular phase is increased.

Next, the wire rod is water-cooled and then wound.

According to one example, at the time of winding, the coiling temperature may be 900 DEG C or less. If it exceeds 900 ° C, ductility may deteriorate due to coarsening of the austenite grains.

Next, the wound wire rod is cooled.

When the wire having the composition described above is cooled at a uniform rate of about 1 캜 / sec, the (Fe, Mn) ₂₃ C ₆ carbide is formed after being transformed from the FCC single phase to BCC. In this case, since the temperature transformed to BCC is about 500 ° C, the temperature is slowly cooled (primary cooling) at a rate of 1 ° C / sec or less (except 0 ° C / sec) _It is preferable to quench (secondary cooling) at a rate of 10 ° C / sec or more up to 200 ° C, which is a temperature range in which ₂₃ C ₆ carbide is formed. This is to suppress the decrease in toughness due to the growth of carbide. On the other hand, when the cooling rate in the primary cooling is excessively low, the productivity tends to decrease to such an extent that the actual operation is difficult. Therefore, considering the productivity, the cooling is preferably performed at a rate of 0.5 deg.

Hereinafter, a method for manufacturing a steel wire, which is another aspect of the present invention, will be described in detail.

First, a wire having the above-mentioned component system and prepared by the above-described method is prepared, the scale formed on the surface of the wire is removed, and the wire is roughly drawn to secure dimensional accuracy.

Generally, on the surface of the wire there is a scale of about 20 to 30 μm thick, which can cause breakage due to scaling during processing. Therefore, it is preferable to remove the scale before machining, for example, by removing hydrochloric acid or sulfuric acid, or mechanical stripping and hydrochloric acid to remove scale.

Then, in order to reduce the unevenness of the diameter of the wire due to the scale removal and to suppress the occurrence of fine cracks, the scale wire is roughly drawn to secure dimensional accuracy.

According to one example, at about freshness, the total amount of reduction may be 2 to 7%. If the total amount of reduction is less than 2%, the surface roughness may not be uniformly controlled. On the other hand, if the total amount of reduction exceeds 7%, the deformation is greatly applied only on the surface to induce the homogeneity of the structure of the tissue, There is a concern.

Next, the wire having the dimensional accuracy secured is rolled to obtain a steel wire.

At this time, the drawing speed is preferably 100 to 300 m / m. If the drawing speed is less than 100 m / m, the productivity is excessively reduced. If the drawing speed is more than 300 m / m, the possibility of occurrence of hot cracks becomes too high.

The total amount of reduction is preferably 66% or more. This is for securing the target strength. At this time, the total amount of reduction can be calculated by the following equation (1).

[Formula 1]

Total reduction amount (%) = {1- (cross-sectional area of fresh wire after cross-section / cross-sectional area of wire before wire drawing)} × 100

The steel wire according to the present invention can omit the preheating treatment performed for the miniaturization of the conventional structure. Unlike the conventional method of securing the product characteristics by applying the drawing amount of 40 ~ 70% It is advantageous in that the product competitiveness is excellent because the product characteristics can be secured by merely applying the processing amount and the rolling amount of 50% level.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the description of these embodiments is intended only to illustrate the practice of the present invention, but the present invention is not limited thereto. And the scope of the present invention is determined by the matters described in the claims and the matters reasonably deduced therefrom.

( Example )

A billet having the composition shown in the following Table 1 was prepared, reheated at 1200 ° C for 100 minutes, and then subjected to hot rolling under the condition of a finish rolling temperature of 1050 ° C to obtain a wire rod (Inventive Example 1) having a diameter of 11 mm. Thereafter, the wire rod was water-cooled, then rolled at 800 ° C, primary-cooled to 500 ° C at a rate of 1 ° C / sec, and secondarily cooled to 200 ° C at a rate of 10 ° C / sec. At this time, the tensile strength of the secondarily cooled wire was 1470 MPa. On the other hand, FIG. 1 (a) is a photograph showing the surface of the wire according to Inventive Example 1 observed.

Thereafter, the scale was removed, and the steel wire was rolled by hot rolling at a total reduction of 5% and a total reduction of 50% without any additional heat treatment. At this time, the tensile strength of the steel wire was 1615 MPa, and the elongation was 12.9%.

ingredient C Si Mn B N P S Range (% by weight) 0.1 0.1 6 0.0015 0.005 0.009 0.010

For comparison, a 16 mm wire rod (Comparative Example 1) was produced using commercially available carbon steel (0.72 wt% C-0.5 wt% Si-0.75 wt% Mn). At this time, the coiling temperature was set to 900 占 폚, and the cooling rate after winding was kept constant at 8 占 폚 / sec. At this time, the tensile strength of the cooled wire rod was 980 MPa. On the other hand, FIG. 1 (b) shows the surface of the wire according to Comparative Example 1 observed.

Thereafter, the scale was removed, heated at 950 ° C for 1 minute in a high-temperature furnace, and held at 500 ° C for 1 minute. Thereafter, the steel wire was drawn with a total reduction amount of 62%. At this time, the tensile strength of the steel wire was 1610 MPa and the elongation was 11.1%.

Claims (12)

The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.1 to 0.2% of C, 0.1 to 0.5% of Si, 5 to 8% of Mn, 0.03% or less of P, 0.03% or less of S, 0.001 to 0.003% The remainder Fe and unavoidable impurities, and including martensite of not less than 90% by area (including 100% by area) and having a diameter of 12 mm or less (excluding 0 mm).
The method according to claim 1,
Wherein the mean circle equivalent diameter of the martensite is not more than 15 占 퐉.
delete The method according to claim 1,
A wire having a tensile strength of 1400 MPa or more.
The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.1 to 0.2% of C, 0.1 to 0.5% of Si, 5 to 8% of Mn, 0.03% or less of P, 0.03% or less of S, 0.001 to 0.003% Reheating the billet comprising the remainder Fe and unavoidable impurities;
Hot-rolling the reheated billet to obtain a wire rod having a diameter of 12 mm or less (excluding 0 mm);
Winding the wire rod;
Cooling the wound wire rod to 500 to 850 DEG C at a rate of 1 DEG C / sec or less (excluding 0 DEG C / sec); And
Secondarily cooling the primary cooled wire to 200 DEG C at a rate of 10 DEG C / sec or more;
Wherein the wire rope is made of a metal.
6. The method of claim 5,
Wherein the reheating temperature during reheating of the billet is 1150 to 1250 ° C.
6. The method of claim 5,
Wherein the reheating time at the time of reheating the billet is 90 to 150 minutes.
6. The method of claim 5,
Wherein the hot rolling temperature of the reheated billet is 1000 占 폚 or higher.
6. The method of claim 5,
Wherein the winding temperature of the wire rod is 900 DEG C or less.
6. The method of claim 5,
And the cooling rate during the primary cooling of the wound wire is 0.5 to 1 占 폚 / sec.
The steel sheet according to any one of claims 1 to 3, wherein the steel sheet contains 0.1 to 0.2% of C, 0.1 to 0.5% of Si, 5 to 8% of Mn, 0.03% or less of P, 0.03% or less of S, 0.001 to 0.003% Reheating the billet comprising the remainder Fe and unavoidable impurities;
Hot-rolling the reheated billet to obtain a wire rod having a diameter of 12 mm or less (excluding 0 mm);
Winding the wire rod;
Cooling the wound wire rod to 500 to 850 DEG C at a rate of 1 DEG C / sec or less (excluding 0 DEG C / sec); And
Secondarily cooling the primary cooled wire to 200 DEG C at a rate of 10 DEG C / sec or more;
Removing a scale formed on a surface of the secondarily cooled wire, and drawing the wire to secure dimensional accuracy; And
A step of subjecting the wire material having the dimensional accuracy to a rolling speed of 100 m / m or more at a drawing speed to a total reduction amount of 66% or more to obtain a steel wire;
Wherein the steel wire is manufactured by a method comprising the steps of:
12. The method of claim 11,
Wherein the total amount of reduction is about 2 to 7% at the time of drawing.

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